Predetermined torque release wrench



Sept. 17, 1968 A. G. LOOFBOURROW 3,401,754

PREDETERMINED TORQUE RELEASE WRENCH 2 Sheets-Sheet 1 Filed April 11,1967 MM m m 3 %M M mm M M 5 P 1968 A. G. LOOFBOURROW 3,401,754

PREDETERMINED TORQUE RELEASE WRENCH Filed April 11, 1967 2 Sheets-Sheet2 United States Patent 3,401,754 PREDETERMINED TORQUE RELEASE WRENCHAlan G. Loofbourrow, Bloomfield Hills, Mich., assignor to ChryslerCorporation, Highland Park, Mich., a corporation of Delaware Filed Apr.11, 1967, Ser. No. 629,970 Claims. (Cl. 173-12) ABSTRACT OF THEDISCLOSURE A motor driven torque wrench having a torque arm laterallyextending from the motor housing. The torque arm is mounted so as to becapable of movement at some predetermined torque level which movementactuates a motor control switch. The switch opens an electrical circuitwhich breaks the power supply to the motor thereby causing the torquewrench to shut olf.

Background of the invention The present invention relates to a torquetransmitting device for tightening a fastening member, such as a nut,bolt or screw to a predetermined torque. This device is of simpleconstruction since it employs a minimum of components and, yet, can beeasily adjusted to provide a wide range of torque values. Moreover, itsconstruction provides for a constant and low frictional resistance ofits moving components thereby providing for extremely accurate andconstant torque values over a long period of time.

Although torque wrenches find wide application in industry, heretoforeknown wrenches have suffered from certain disadvantages which limittheir utility. For example, most torque limiting wrenches include aloadengaging member and mechanism which will undergo pivotal or slidingmovement so as to release the loadengaging member when a certain torquelevel is reached. The moving members of the release mechanism, however,are generally supported by complicated or delicate bearing means, pivotaxes, etc. which are readily susceptable to wear from even minimalnormal use of the wrench, thereby giving rise to varying frictionalresistances which result in inaccurate torque values. To minimize suchvariable resistance problems, wrenches have been developed wherein theload-engaging member is linked to a lever arm which in turn is held in anormally fixed position by means of a magnet. In these wrenches, whensome predetermined torque is exceeded, the lever arm is pulled away fromthe magnet thereby allowing the loadengaging member to slip or release.Such systems have not achieved wide spread commercial acceptance,however, due to several problems associated therewith. Thus, such wrenchsystems generally have a narrow torque value range since the magnetholds the lever arm with a constant force. Since a fixed range of torquevalues is undesirable, it has been proposed to provide moveablefulcru-ms whereby the force required to separate the lever arm from themagnet can be varied. However, this adds to the complexity and cost ofthe wrench and introduces operational problems in that the adjustment ofthe fulcrum so as to achieve different torque values generally requiresat least partial disassembly of the wrench. Moreover, calibration of thewrench is difficult since movement of the lever arm relative to themagnet occurs in a direction transverse to the length of the housing,and therefore, extremely slight adjustments in the position of thefulcrum result in substantial variation in the force required to unseatthe lever arm from the magnet.

3,401,754 Patented Sept. 17, 1968 ice Summary of the invention From theforegoing, it will be recognized that a torque wrench is needed which iscapable of providing a relatively large range of torque values and, yet,is simple in construction, inexpensive to manufacture and which affordsextremely accurate results each time that it is used.

Accordingly, it is an object of this invention to provide a novel andimproved device for applying a measured amount of torque to anotherstructure.

A further object is to provide a torque wrench which is constructed andarranged to provide a range of torque values and which is capable ofsimple and accurate calibration.

Yet another object is to provide a torque-limiting wrench incorporatinga simple, rugged mechanism having a low and constant frictionalresistance 'for releasing the loadengaging member of the wrench uponreaching a predetermined torque value.

Other objects and advantages of the present invention will becomeapparent from a further 'reading of the description and the appendedclaims.

Briefly, the apparatus of this invention comprises a drivenload-engaging member which is supported by a housing that is adapted forpivotal movement in response to the load engaging member reaching apredetermined torque value. An arm member extends outwardly from thehousing and is in engageable relationship with control means forshutting off the driven load-engaging member. The arm member isrestrained from actuating the control means, so as to shut olf theload-engaging member, by resilient means, and the amount of torquerequired to effect such shut oif can be easily and quickly varied bysimple adjustment of the resilient means. The torque wrench of thisinvention is constructed such that there is a need for only one pivotconnection as between the various components thereof. Accordingly,frictional resistance and wear factors which have plagued heretoforeknown torque wrenches are reduced to a minimum in the apparatus of thisinvention thereby providing a torque wrench of exceptional accuracy andlong life.

Description of the drawings In the accompanying drawings, in which oneof various possible embodiments is illustrated,

FIGURE 1 is a top view of a torque wrench constructed in accordance withthe invention with portions of the outer skin broken away to revealdetails of internal structure;

FIGURE 2 is a rear-elevational view looking in the direction of line 2-2of FIGURE 1 with portions of the outer skin broken away to showdetailsof internal structure;

FIGURE 3 is a side sectional view taken along the line 33 of FIGURE 1;

FIGURE 4 is a side sectional view taken along line 44 of FIGURE 1; and

FIGURE 5 is a schematic electrical circuit diagram for one embodiment ofthe invention.

Like parts are indicated by corresponding reference charactersthroughout the several views of the drawing.

Description of the preferred embodiment The torque wrench of thisinvention is shown in FIG- URES 1-4 and comprises, as seen withparticular reference to FIGURE 1, a casing or frame, indicated generallyby reference numeral 10, which forms a hollow body, having top, bottomand side walls closed by a removable cover plate 12 held in position byfastening means such as screws 14. Handle members 16 are threadedlysecured to the side wall portion of frame 10. A motor 18 is partiallydisposed within the hollow frame and is supported therein as hereafterdiscussed. Motor 18 is illustrated as being air driven although it willbe appreciated that other types of motors could be employed, such aselectric motors. A rotatable shaft or spindle 20 extends from and isdriven by the motor and is provided with an endportion 22 which servesto retain frictionally on the load-engaging shaft 20 any suitable toolwhich it is desired to mount thereon, such as a socket wrench or screwdriver for engaging a screw, bolt, nut or other member which is de siredto be tightened to a predetermined degree of torque.

In the illustrated embodiment, motor 18, as is seen with reference toFIGURE 1, is driven by compressed air which is supplied to the wrenchvia line 24 and which is interconnected with wrench air line 26 by meansof connector 28. Air flow for operating the torque wrench is controlledby solenoid valve 30 which is interconnected with motor 18 by air line32. Solenoid valve 30 is opened and closed in response to control meanscapable of being actuated by the user of the torque wrench, such asswitch 34 which is provided with push button 36 located in handle 16.

As best seen in FIGURE 2, motor 18 is supported by a housing 38 which isgenerally in the form of a collar or C-clamp member which substantiallysurrounds a portion of the peripheral surface of motor 18. Fasteners 40serve to securely interconnect the motor 18 and housing 38 for unitarymovement. Housing 38 is pivotally mounted for pivotal movement withrespect to frame 10 by means of a fulcrum member 42 which is provided ateach of its opposite end portions (FIGURE 3) with knife-edge 44 and 46.Fulcrum member 42 is secured to frame 10 by suitable fastening means asscrews 48. A member is secured to housing 38 by fasteners 52 andcooperates with fulcrum 42 by means of recessed or notch portions 54 and56 at each of its ends which engage and cradle knife edges 44, 46,respectively. As best seen with reference to FIGURES 1 and 3, the motorand housing 38 are prevented from substantial longitudinal slidingmotion along knife edges 44, 46 by means of pins 58 which extend throughmember 50 so as to be engageable with the knife edge portions of fulcrummember 42.

To release the load-engaging shaft 20 upon its reaching a certain torquelevel, additional control means spaced from housing 38 are provided.Thus, as best seen in FIG- URE 4, a switch 60 having push button 62 issecured to frame 10 by fasteners 64 and is interconnected, along withswitch 34, in a circuit, hereinafter described, for controlling theoperation of solenoid valve 30.

Switch 60 is actuated in response to movement of an arm member 66 whichextends outwardly from housing 38. Thus, one end portion 66a of armmember 66 is disposed within a slot formed in housing 38 and is securedthereto by fasteners 68. Secured by pins 70 to the opposite end of armmember 66 is a clevis member 72 having a threaded bore portion 74extending therethrough. A finger 76 extends radially outwardly fromclevis member 72 so as to be engageable with push button 62 of switch60.

To position and control movement of the arm member 66, resilient meansare provided which resist pivotal movement of the arm member. Thus, astop member 78 is threadedly engaged with bore 74 and has a surface 80which normally engages frame 10 due to the biasing action of a spring82. As seen with reference to FIGURE 4, one end of spring 82 is disposedwithin a recess 84 provided in stop member 78 so as to minimize spacerequirements and the opposite spring end is supported by a threaded post86 which is threadedly carried by frame 10 and in axial alignment withstop member 78. An adjustment nut 88 threadedly engages post 86 so as toenable easy and quick regulation of spring pressure, thereby providingfor adjustment of the torque release value of the wrench. In order topermit calibration of the torque wrench to desired torque releasevalues, stop member 78 is provided with a bore 90 which is axiallyaligned with an opening 92 in frame 10. As seen with reference to FIGURE4, calibration is accomplished by inserting the stem 94 of a knownweight 96 through opening 92 and into bore 90 so as to load the armmember 66. Spring 82 is then adjusted through manipulation of post 86 toprovide the desired torque release setting.

In operation, spring 82 biases stop member 78 into engagement with frame10 and maintains knife edges 44, 46 in firm engagement with notchportions 54, 56. Finger 76, as seen in FIGURE 4, is accordingly, held incontact with push button 62 so as to close switch 60. The load engagingshaft 20 is engaged with a member to be tightened and the operatoractuates switch 34 by means of push button 36 located in handle 16. Atthis point, as seen with reference to FIGURE 5, current flows through atime relay switch 102, switch 60 and circuit relay control 104. Thecircuit relay control 104 then closes circuit relays 100, and 112 andopens circuit relay 106. Accordingly, the circuit through solenoid valve30 is completed and the solenoid valve opens to permit air to energizemotor 18 and drive shaft 20. At this same time, a time relay 108 isactuated due to the opening of circuit relay 106 and causes switch 102to open after a period, of for example, about one second, so as todisconnect switch 34 from the circuit even in the event push button 36is held depressed.

As the load engaging shaft 20 rotates in a clockwise direction as viewin FIGURE 2, the motor 18 and housing 38, which is securely connected tothe motor, are urged in a counterclockwise direction against thepressure of spring 82. When the desired predetermined degree of torqueis reached, the force of spring 82 is overcome and housing 38 pivotsabout the knife edges 44, 46 and lever arm 66 rotates downward, asviewed in FIGURE 2, thereby opening switch 60. Accordingly, the circuitthrough circuit relay control 104 is opened thereby closing circuitrelay 106 and opening circuit relays 100, 110 and 112 which de-energizessolenoid 30, shutting off motor 18. Spring 82 then causes housing 38 topivot about fulcrum member 42 which carries stop member 78 intoengagement with frame 10 and finger 76 into actuating engagement withswitch 60 thereby allowing the cycle to be repeated. It will be notedupon examination of the circuit shown in FIGURE 5, that it is necessaryfor the operator to release the push button 36 of switch 34 and thendepress it in order to actuate the motor after the desired torque valuehas been reached and arm member 66 actuated switch 60. This is desirableto prevent actuation of the torque wrench upon its being removed fromthe load in the event the operator has maintained push button 36 in adepressed position. As an additional safety factor, a wrench shut offswitch, such as switch 114 (FIGURE 1) can be provided to completelyde-energize the entire circuit arrangement as shown in FIGURE 5 therebypreventing accidental actuating of the torque wrench.

The torque wrench described hereinabove has been used with great successand found to provide extremely accurate and uniform torque values.Moreover, it is readily adaptable to provide a wide range of torquevalues, such range only being limited by the size and quality ofconstruction of its components. The size and weight of the wrench arenaturally determined primarily by the conditions under which it will beused; however, due to its generally symmetrical shape the wrench can beconstructed to provide any range of torque values without fear of weightproblems since the wrench can readily be supported by cable 116(FIGURE 1) which is part of a counter balance arrangement (not shown).

From the foregoing description, it is seen that the torque wrench ofthis invention does not employ, as found in heretofore known wrenches, acomplicated mechanism for releasing the load engaging member at apredetermined torque. The torque wrench employs only a single pivotalconnection as between the 'various components thereof and due to theknife edge construction of this pivot connection it is not subject toany appreciable wear and provides for a minimum of frictionalresistance. Likewise, unlike other torque wrenches there are no catchesor other fittings subject to wear, thereby greatly increasing theworking life and accuracy of the torque device of this invention.

Accordingly, the above-mentioned objects of this invention have beenfulfilled and it will be understood that modifications and variationsmay be effected without departing from the scope of the novel conceptsof the present invention as defined in the appended claims.

I claim:

1. A torque wrench comprising a frame member, a housing, a rotatableshaft supported by the housing and having a portion adapted to beoperatively connected in torque transmitting relation to a member to betightened, driving means for rotating said shaft, control meanseffective at times to actuate said driving means, additional controlmeans spaced from said housing and being effective at times to deactuatesaid driving means, an arm member extending from said housing and havinga portion in engageable relationship with said additional control means,and pivot means for allowing pivotal movement of said housing withrespect to said frame, said pivotal movement of said housing beingoperative to effect simultaneous pivotal movement of said arm member,and said additional control means being adapted to be activated inresponse to the movement of said arm member.

2. A torque wrench according to claim 1 wherein said pivot meanscomprises a fulcrum having at least one knife edge, and wherein saidhousing pivots about said knife edge.

3. A torque wrench according to claim 1 wherein said control meanscomprises an electrical circuit and a first switch means operative toopen and close said circuit, and wherein said additional control meanscomprises a second switch means operative to open and close saidcircuit.

4. A torque wrench according to claim 1 including resilient means whichresists pivotal movement of said arm member in a direction opposite tothe direction of rotation of said shaft when said shaft is driven bysaid driving means.

5. A torque wrench according to claim 1 having a stop member disposed soas to limit pivotal movement of said housing and arm member in thedirection of rotation of said shaft when said shaft is driven by saiddriving means, and further having adjustable resilient means normallybiasing at least one of said housing and arm members in said direction.

6. A torque wrench according to claim 5 wherein said stop member iscarried by said arm member so as to be in engageable relationship withsaid frame, and wherein said adjustable resilient means comprises aspring which normally holds said stop member in contact with said frame.

7. A torque wrench according to claim 1 wherein said driving meansconstitutes a motor and said control means comprises an electricalcircuit to actuate the motor and a first switch operative to open andclose said circuit, wherein said additional control means comprises asecond switch which is spaced from said housing and operative to openand close said circuit in response to movement of said arm member,wherein said pivot means comprises a fulcrum having at least one knifeedge, said fulcrum being carried by one of said housing and framemembers, wherein one of said frame and arm members carries a stop memberto limit pivotal movement of said arm member in the direction ofrotation of the shaft when said shaft is driven by said motor, andwherein said wrench includes adjustable resilient means, said arm memberbeing carried by said housing and being normally biased in saiddirection of shaft rotation by said adjustable resilient means.

8. A torque wrench according to claim 1 wherein the driving meanscomprises a motor, said motor being supported by said housing, whereinthe pivot means comprises a fulcrum having a knife edge which is carriedby said frame member, wherein said control means comprises an electricalcircuit and a first switch operative to open and close said circuit,said wrench further including a stop member disposed so as to limitpivotal movement of said housing in the direction of rotation of theshaft when said shaft is rotated by said rotor, and adjustable resilientmeans acting on the arm member so as to resist pivotal movement of saidarm in a direction opposite to the direction of rotation of said shaftwhen said shaft is driven by said motor, said arm member being carriedby said housing and extending outwardly therefrom in a directiongenerally normal to the axis of rotation of said shaft.

9. A torque wrench according to claim 8 wherein the housing is providedwith notch means disposed so as to cooperate with said knife edgeportion of said fulcrum, said fulcrum and housing being positioned suchthat said knife edge portion is cradled in said notch means.

10. A torque wrench according to claim 9 wherein said stop member isspaced from said housing and carried by said arm member so as to beengageable with said frame, and wherein said adjustable resilient meansis spaced from said housing and normally holds said stop member incontact with said frame.

References Cited UNITED STATES PATENTS 1,938,720 12/1933 Preble 192-1502,627,770 2/1953 Hautau et al 8152.4 2,857,793 10/1958 Peras 8l52.42,973,066 2/1961 Eddy 192-150 X MYRON C. KRUSE, Primary Examiner.

